Research Of The Effect To Ballast Bed Breakage And Mechanical Properties By Tamping And Dynamic Stabilizing Operation

As a granular structure,a series of diseases will occur in ballast bed under the dynamic load of high-speed train,such as ballast pulverization,abrasion,crushing,ballast subsidence groove,ballast bed deformation,flow collapse,etc.This will change the geometry of ballast track,deteriorate the smoothness of track,intensify the dynamic effect between wheel and rail,and seriously affect the stability,comfort and safety of train operation.Large-scale maintenance machine can effectively adjust the track geometry,improve ballast elasticity and service performance.However,the impact of tamping tine will cause the breaking of ballast particles,changing of ballast gradation,decreasing of ballast uniformity and mechanical properties.Therefore,how to scientifically and reasonably use the machine for maintenance operation is the key to ensure high smoothness and stability of ballast track.The size and shape of gravel ballast are different,and the contact forms between particles are varied,which cause the mechanical behavior under the effect of large-scale maintenance machine to be extremely complex.Besides,there are kinds of machine operating parameters.As a result,the maintenance work of ballast bed is mostly based on experience,and we haven’t formed a scientific theoretical system to effectively guide the machine operation yet.Based on the coupling algorithm of discrete element and multi-body dynamics,this paper solved the scientific problem that traditional discrete element method can not accurately simulate the interaction between ballast and sleeper.By means of theoretical analysis,laboratory test and numerical simulation,macroscopic and mesoscopic effect of ballast breaking and mechanical properties under the function of large-scale maintenance machine were atudied.The main research work of this paper is summarized as follows:1.A refined model of fragile ballast and a coupled EDEM-ADAMS model were constructed.Laser scanning method was used to reconstruct the three-dimensional shape of ballast particles,and the API module which can generate spatial lattice was developed independently,which realized the fine simulation of ballast particles.On this basis,the coupling model of machine-ballast bed was built by using the coupling algorithm of discrete element and multi-body dynamics.According to the basic working principle of tamping and stabilizing operation,the authentic simulation of machine was achieved in the model.Based on the field measured data,the train dynamic load was effectively fitted,and the accuracy of the numerical simulation model was verified.2.Study on ballast breaking under the effect of large-scale maintenance machine.Based on fractal method,the fractal evolution,stress distribution characteristics,changing of ballast strength and energy were studied by combining theoretical analysis,laboratory test and numerical simulation.The mechanism of ballast breaking was revealed.The dynamic response of ballast particles and the regularity of ballast breaking evolution during machine operating were analyzed.The influence of particle strength,shape and gradation on ballast breaking was studied.Finally,the suggestions for ballast type selection in ballast bed were put forward.3.Study on the mechanism of ballast bed under the effect of large-scale maintenance machine.The moving law of ballast and the variation characteristics of compactness in the process of machine operating were analyzed.The effects of machine operation on lateral resistance,longitudinal resistance and supporting stiffness of ballast bed were studied from macro and micro perspectives respectively.Finally,the mechanism of ballast bed under the effect of large-scale maintenance machine was revealed.4.Study on the influence of working parameters,working procedures and rolling of heavy haul train on the quality of ballast bed.The influences of tamping and stabilizing parameters on mechanical properties of ballast bed were systematically studied,and optimization suggestions for the parameters of machine operation were put forward.The effects of tamping times,stabilizing times and combination mode on the quality of ballast bed were explored,and the optimization scheme of large-scale machine operating process was proposed.The evolution law of ballast bed quality under the rolling of heavy haul train was analyzed.Finally,ballast track maintenance and repairing operating optimization system was formed,which effectively ensures the safety of train operation.